#include <iostream>
using namespace std;
int kai (int,int,int);
int main ()
{
	int x,y,z;
	cin>>x>>y>>z;
	cout<<kai (x,y,z);
	return 0;
}
int kai (int a,int b,int c)
{
	if (a<=0||b<=0||c<=0)
		return 1;
	else if (a>20||b>20||c>20)
		return kai (20,20,20);
	else if (a>b&&b>c)
		return kai(a,b,c-1)+kai(a,b-1,c-1)-kai(a,b-1,c);
	else
		return kai(a-1,b,c)+kai(a-1,b-1,c)+kai(a-1,b,c-1)-kai(a-1,b-1,c-1);
}
